A bleach activator can generally be described as an organic peroxyacid bleach precursor which in the bleaching solution reacts with an inorganic peroxygen bleaching agent with release of the organic peroxyacid. Peroxygen bleaches are especially effective at removing oxidizable stains from hard surfaces or fabrics at temperatures less than about 60.degree. C.
Water-soluble bleach activators in particular have rapid dispersibility in wash or bleach solution as well as the ability to exhibit surface bleaching. Described in detail in U.S. Pat. No. 4,412,934, Chung et al., issued Nov. 1, 1983 are water-soluble bleach activators, having the general formula: ##STR1## wherein R is an alkyl group containing from about 5 to about 18 carbon atoms wherein the longest linear alkyl chain extending from and including the carbonyl carbon contains from about 6 to about 10 carbon atoms and L is a leaving group, the conjugate acid of which has a pKa in the range of from about 6 to about 13.
However, water-solubility exacerbates bleach activator stability problems caused by interaction between moisture and peroxygen bleaching agent during prolonged storage in the bleach or detergent composition. To address this, U.S. Pat. No. 4,681,695, Divo, issued July 21, 1987 teaches a bleach activator composition in the form of spray-dried granules having an inner core comprising water-soluble organic peroxyacid bleach precursor and a surface coating comprising a water-soluble or water-dispersible inorganic hydratable material. A process of making the composition by forming a crutcher slurry mix of the bleach precursor and hydratable material, adjusting the pH between about 3 and 8, and spray drying is also disclosed.
U.S. Pat. No. 4,536,314, Hardy et al., issued Aug. 20, 1985 teaches detergent compositions, detergent additive products and bleaching compositions containing non-linear aliphatic peroxyacid bleach precursors of formula: ##STR2## where L is a leaving group of defined formula whose conjugate acid has a pKa of from 6 to 13 and ##STR3## is a non-linear acyl group, the carboxylic acid derivative of which has a logP.sub.oct in the range from 1.9 to 4.0 (where P.sub.oct is the partition coefficient between octanol and water). New precursor compounds are provided in which ##STR4## is a C.sub.7 -C.sub.17 branched aliphatic acyl group containing a linear chain of at least 5 carbon atoms extending from and including the carbonyl carbon wherein the branching is on at least the 2- and/or 3-carbon atom. These non-linear aliphatic peroxyacid precursors provide effective bleaching of oxidizable stains without generating unattractive odors.
U.S. Pat. No. 4,009,113, Green et al., issued Feb. 22, 1977, discloses granular compositions comprising from about 40% to about 80% of a bleach activator and an inert carrier material such as long chain fatty acids or esters wherein said precursor is substantially evenly distributed with said precursor compound to form a composite particle. The particle has an outer protective layer which can consist of, for example, polyvinyl alcohol. It is stated that such compositions have both good storage stability and dispersibility in the wash water.
Lastly, U.S. Pat. No. 4,486,327, Murphy et al., issued Dec. 4, 1984, discloses bleach activator bodies comprising specific peroxygen bleach activators and select binder materials. When formulated in such bodies the peroxygen bleach activators have excellent storage stability and maintain excellent dispersibility in wash water.
It has been found, however, that a problem can be encountered when coloring the bleach activators of Chung et al. (see above), which have been stabilized in the manner of Murphy et al. (see above) and formed into extrudates. When an aqueous solution containing dye or pigment is applied to the bleach activator extrudates, a significant number of them may stick together, forming undesirable agglomerates. Apparently because these sizable agglomerates capture some of the dye or pigment, the bleach activator extrudates are not as evenly or as brightly colored as they would be without agglomerates. In addition to being an appearance negative, heavily dyed agglomerates in product increase the risk of fabric damage by the dye. The agglomerates must be sifted out before the bleach activator extrudates can be used. The extrudates are then admixed with, for example, base detergent granules to form a colored or speckled final granular detergent product.
This problem has now been solved by the instant discovery that incorporating water-soluble hydratable material into the aqueous solution containing the stable water-soluble dye or water-dispersible pigment, followed by distributing the aqueous solution on the surface of the stabilized bleach activator extrudates, preferably in a substantially even manner such as by spraying the solution, results in evenly colored, free-flowing bleaching activator extrudates. The extrudates are then admixed in a final granular detergent product comprising a peroxygen bleaching compound capable of yielding hydrogen peroxide in an aqueous solution. The molar ratio of hydrogen peroxide to bleach activator compound in the final product is greater than about 1.5.